Germanium is used widely for lenses and windows in thermal imaging, FLIR applications, as germanium viewports. Its high index of refraction (about 4) makes it of particular interest. Useful transmission range of Germanium windows is from 2 to 13µm. Germanium is opaque in the visible.
Custom germanium windows ,lenses and prisms are available in any size and configuration. Anti-reflection coatings can be applied for 2-14µm or 8-12µm (BBAR coating or DLC/BBAR) depending on your custom application.
Germanium windows specifications:
|
|
Standard precision |
High-precision |
|
Dimension Tolerance |
φ5-250mm+0/-0.2 |
φ3-350mm+0/-0.2 |
|
Thickness Tolerance |
1-50mm+/-0.1 |
1-50mm |
|
Parallelism |
1 arc minute |
10 arc seconds |
|
Surface Quality |
60/40 |
20/10 |
|
Flatness |
N<λ/2@633nm（at 50mm） |
N<λ/10@633nm（at 50mm） |
|
Clear Aperture |
>90% |
>95% |
|
Chamfer |
Protected <0.5mmx45deg |
Protected <0.5mmx45deg |
Germanium properties
Chemical Formula
Ge
Crystal Form
Poly or Single Crystal
Crystal Class
Cubic
Resistivity, Ohm*cm
5-40
Lattice Constant, Å
5.66
Molecular Weight
72.60
Density, g/cm3 at 300 K
5.33
Dielectric Constant for 9.37 x 109 Hz at 300 K
16.6
Melting Temperature, K
1210
Thermal Conductivity, W/(m K) at 293 K
59
Thermal Expansion, 1/K at 298 K
6.1 x 10-6
Specific Heat, cal/(g K) at 273-373 K
0.074
Debye Temperature, K
370
Bandgap, eV
0.67
Solubility in water
None
Knoop Hardness, kg/mm2
800
Mohs Hardness
6.3
Young's Modulus, GPa
102.66
Shear Modulus, GPa
67.04
Bulk Modulus, GPa
77.86
Poisson's Ratio
0.278